Process for separation of substituted benzene isomers

ABSTRACT

A substituted benzene isomer mixture containing a meta-substituted benzene or 1,3,5-substituted benzene is contacted with an adsorbent of a faujasite type zeolite containing a Ag cation and/or a Cu cation, whereby the meta-substituted benzene or 1,3,5-substituted benzene is separated and recovered as a raffinate component.

This is a division of application Ser. No. 515,927, filed July 20, 1983,now U.S. Pat. No. 4,571,441.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a process for separating a meta-substitutedbenzene or 1,3,5-substituted benzene from a substituted benzene isomermixture containing a meta-substituted benzene or 1,3,5-substitutedbenzene nuclearly substituted with a methyl, ethyl or hydroxyl group ora halogen atom.

2. Description of the Prior Art

m-Chlrotoluene among chlorotoluene (hereinafter referred to as "CT")isomers, m-dichlorotoluene among dichlorotoluene (hereinafter referredto as "DCB") isomers and 3,5-xylenol among xylenol (hereinafter referredto "XYOH") isomers are important as intermediate substances foragricultural chemicals and medicines, and m-diethylbenzene amongdiethylbenzene (hereinafter referred to as "DEB") isomers is valuable asa desorbent or an intermediate substance for a crosslinking agent.However, considerable difficulties are encountered in separation ofthese compounds by distillation because their boiling points are veryclose to those of their isomers.

If there is available an adsorbent capable of adsorbing a specificisomer selectively, separation of isomers will be accomplished at a highefficiency economically advantageously. An isomer capable of beingstrongly adsorbed in the adsorbent is selectively adsorbed in theadsorbent to be thereby separated as an extract component, and an isomercapable of being weakly adsorbed in the adsorbent is weakly adsorbed inthe adsorbent to be thereby separated as a raffinate component. Thus,the isomer mixture is separated into the respective isomers.

U.S. Pat. No. 4,356,331 discloses a process in which a para-isomer isselectively adsorbed and separated from an alkyl phenol isomer mixtureby using a zeolite of the Y type.

Furthermore, European Patent Application No. 81303609.2 discloses aprocess in which a para-isomer is selectively adsorbed and separatedfrom a halogenated toluene isomer mixture by using a zeolite of the Ytype.

However, these prior art references do not teach separation and recoveryof meta-isomers.

U.S. Pat. No. 4,254,062 discloses separation of dichlorotoluene isomersby using a zeolite of the X or Y type, but separation of a1,3,5-substituted isomer is not taught at all.

U.S. Pat. No. 4,124,770 discloses a process in which xylenol isseparated from a mixture of xylenol and cresol by using a zeolite, butseparation of a xylenol isomer mixture or cresol isomer mixture is nottaught at all.

SUMMARY OF THE INVENTION

It is a primary object of the present invention to provide a process inwhich a meta-substituted benzene or 1,3,5-substituted benzene asdescribed above is separated at a high purity from a starting mixturecontaining isomers thereof at a high efficiency by utilizing anadsorptive separation technique.

More specifically, in accordance with the present invention, there isprovided a process for separating a meta-substituted benzene or1,3,5-substituted benzene from a substituted benzene isomer mixturecontaining a meta-substituted benzene or 1,3,5-substituted benzenenuclearly substituted with a methyl, ethyl or hydroxyl group or ahalogen atom, wherein the isomer mixture is contacted with a faujasitezeolite type adsorbent containing a Ag cation and/or a Cu cation wherebythe meta-substituted benzene or 1,3,5-substituted benzene is separatedand recovered as a raffinate component.

DETAILED DESCRIPTION OF THE INVENTION

Typical instances of the meta-substituted benzene to which the presentinvention is applied are m-CT, m-DCB and m-DEB, and typical instances ofthe 1,3,5-substituted benzene are 3,5-XYOH and 1,3,5-trimethylbenzene.

The faujasite type zeolite that is used in the present invention is acrystalline aluminosilicate represented by the following formula:

    0.9±0.2M.sub.2/n O:Al.sub.2 O.sub.3 :xSiO.sub.2 :yH.sub.2 O

wherein M stands for a cation, and n indicates the valency of the cationM.

The faujasite type zeolite is classified into X and Y types. In the Xtype, x is a number of 2.5±0.5, and in the Y type, x is a number of from3 to 6. In the present invention, a zeolite of the Y type in which x,that is, the SiO₂ /Al₂ O₃ ratio, is in the range of from 3 to 6 ispreferred. Zeolites of the Y type are described in detail in U.S. Pat.No. 3,130,007.

In the above formula, y differs according to the degree of hydration.

M is a cation. Ordinarily, a zeolite of the Y type in which M is sodiumis available. In the present invention, silver and/or copper should beintroduced as the cation into the adsorbent by the ion exchange. Any ofknown ion exchange processes can optionally be adopted. Ordinarily, theion exchange is effected with an aqueous solution containing a nitrateof a required cation. Of course, an aqueous solution containing otherwater-soluble salt such as a chloride instead of the nitrate may beused.

When a faujasite type zeolite containing silver and/or copper as thecation is prepared, it is preferred that a sodium or potassium typefaujastic be used as the starting material to be subjected to the ionexchange.

The faujasite type zeolite adsorbent may contain a cation other thansilver and copper. For example, a metal of the group IA, IIA, IIIA orIVA or a proton may be contained. K and Na are especially preferred asthe cation other than silver and copper.

The proportions of these cations differ according to the kind of themeta-substituted benzene or 1,3,5-substituted benzene to which thepresent invention is applied.

In case of m-CT, m-DCB or m-DEB, the Ag cation preferably occupies 5 to90 mole% of all the cations and the K cation preferably occupies 10 to95 mole% of all the cations. It is especially preferred that theproportion of the Ag cation be 10 to 50 mole% and the proportion of theK cation be 50 to 90 mole%. In case of 3,5-XYOH, the Ag and/or Cu cationpreferably occupies 5 to 100 mole%, especially 15 to 100 mole%, of allthe cations.

The adsorptive separation of a meta-substituted benzene or1,3,5-substituted benzene by using the specified adsorbent according tothe present invention may be accomplished by a chromatographicseparation method or a continuous adsorptive separation method using asimulated moving bed.

According to the adsorptive separation method using a simultated movingbed, a plurality of adsorbing chambers filled with an adsorbent are usedand the following adsorption operation, concentration operation anddesorption operation described below are continuously carried out in acycle as the basic operations.

(1) Adsorption Operation

The starting mixture is contacted with the adsorbent whereby thecomponent capable of being strongly adsorbed is selectively adsorbed.The remaining component capable of being weakly adsorbed is recovered asthe raffinate component together with a desorbent described below.

(2) Concentration Operation

The adsorbent having adsorbed therein the component capable of beingstrongly adsorbed is contacted with a part of an extract describedbelow, whereby the component capable of being weakly adsorbed, which isleft in the adsorbent, is expelled and the component capable of beingstrongly adsorbed is purified.

(3) Desorption Operation

The purified component capable of being strongly adsorbed is expelledfrom the adsorbent by the desorbent, and is recovered as the extractcomponent together with the desorbent.

The intended meta-substituted benzene or 1,3,5-substituted benzene isseparated and recovered as the raffinate component, that is, as thesubstance capable of being weakly adsorbed.

The desorbent used in the above-mentioned adsorptive separation methodor the developer used in the chromatographic separation method ispreferably a compound capable of being easily separated by distillationfrom the intended meta-substituted benzene 1,3,5-substituted benzene.

In the case where the intended substance is m-CT or m-DCB, analkyl-substituted aromatic hydrocarbon or a chlorine-substitutedaromatic hydrocarbon is preferred as the desorbent. Toluene, xylene,dichlorotoluene and chloroxylene are especially preferred.

In the case where the intended substance is m-DEB, toluene, xylene andtrimethylbenzene are especially preferred as the desorbent.

In the case where the intended substance is 3,5-XYOH, oxygen-containingcompounds, for example, alcohols having 3 to 6 carbon atoms such asn-propyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl, alcohol,amyl alcohol and hexanol, and ketones having 4 to 6 carbon atoms such asdiethyl ketone, ethyl isopropyl ketone and diisopropyl ketone, arepreferably used as the desorbent.

In the case where the intended substance is 1,3,5-trimethylbenzene,toluene, xylene and diethylbenzene are preferably used as the desorbent.

Furthermore, n-paraffin, isoparaffin, cycloparaffin or an aromatichydrocarbon may be used as a diluent.

The adsorptive separation is carried out at a temperature of from roomtemperature to 350° C., preferably from 50° to 250° C., under a pressureof from atmospheric pressure to 50 Kg/cm² G, preferably from atmosphericpressure to 40 Kg/cm² G. In the present invention, the adsorptiveseparation may be carried out either in the vapor phase or in the liquidphase. However, in order to prevent occurrence of an undesirable sidereaction in the starting mixture or desorbent, it is preferred that theoperation be carried out at a low temperature in the liquid phase. Ifthe starting mixture containing 3,5-XYOH is solid at the above-mentionedoperation temperature, a hydrocarbon having a low solidification pointmay be used as a solvent.

The process of the present invention will now be described in detailwith reference to the following examples.

In the examples, the adsorbing characteristic of the adsorbent isexpressed by the following adsorptive selectively α: ##EQU1##

In the above formula, S designates the adsorbed phase and L designatesthe liquid phase equilibrated with the adsorbed phase.

If the value α is larger than unity, the component A is selectivelyadsorbed, and if the value α is smaller than unity, the component B isselectively adsorbed. If the value α is more larger than unity (or issmaller than unity and closer to zero) in the adsorbent, the adsorptiveseparation of the components A and B becomes easier.

EXAMPLE 1

Alumina sol was added as a binder to a powder of a zeolite of the Na-Ytype ("SK-40" supplied by Union Carbide Corporation) in an amount of 10%by weight as Al₂ O₃. A granulation product having a size of 24 to 32mesh was obtained by extrusion molding from the mixture. The granulationproduct was dried at 100° C., calcined at 500° C. for 1 hour and thentreated with an aqueous solution of potassium nitrate to replace morethan 90% of the sodium ion with the potassium ion and thereby prepare anadsorbent of the K-Y type.

The zeolite of the K-Y type was treated at 60° C. with an aqueoussolution of silver nitrate containing a silver ion in an amountcorresponding to 10 to 60 mole% of the cation K is the zeolite of theK-Y type to prepare an adsorbent of the Ag-K-Y type.

In order to determine the selectivity of this adsorbent of the Ag-K-Ytype for adsorption of chlotoluene isomers, about 2 g of the aboveadsorbent sintered at 500° C. for 1 hour and about 2.5 g of aliquid-phase mixture which comprises chlorotoluene isomers were chargedin an autoclave having an inner capacity of 5 ml and heated at 110° C.for 1 hour while conducting stirring now and then.

A liquid-phase mixture charged comprised n-nonane, p-chlorotoluene,m-chlorotoluene and o-chlorotoluene at a weight ratio of 1:1:1:1.

n-Nonane was added as the internal standard substance for thegas-chromatographical analysis, and it was substantially inactiverelatively to the adsorption under the experimental conditions. Thecomposition of the liquid-phase mixture after the contact with theabsorbent was analyzed by the gas chromatography, and the adsortionselectivities for the chlorotoluene isomers were calculated according tothe above-mentioned formula. The obtained results are shown in Table 1.

                  TABLE 1                                                         ______________________________________                                                Amount of Ag Ion in Treating                                          Run No. Liquid [Ag/(K--Y) molar ratio]                                                                     α.sub.o/m                                                                       α.sub.p/m                          ______________________________________                                        1       0.1                  1.30    1.80                                     2       0.2                  1.35    1.62                                     3       0.3                  1.50    1.55                                     4       0.4                  1.55    1.45                                     5       0.5                  1.50    1.40                                     6       0.6                  1.45    1.27                                     ______________________________________                                    

EXAMPLE 2

The adsorbent No. 4 shown in Table 1 of Example 1 was subjected to theion exchange at a solid/liquid ratio of 5 by using an aqueous solutioncontaining 7.8% by weight of potassium nitrate and an aqueous solutioncontaining 0.6% by weight of ammonium sulfate.

The adsorptive selectivities of the resulting adsorbent for thechlorotoluene isomers were determined in the same manner as described inExample 1. It was found that α_(p/m) was 1.57 and α_(o/m) was 1.52.

COMPARATIVE EXAMPLE 1

Faujasite type zeolites in which the content of the single cationcomponent was nearly 100% were tested in the same manner as described inExample 1, and the adsorptive selectivities for the chlorotolueneisomers were determined. The obtained results are shown in Table 2.

                  TABLE 2                                                         ______________________________________                                        Adsorbent            α.sub.o/m                                                                      α.sub.p/m                                   ______________________________________                                        Na--Y(SiO.sub.2 /Al.sub.2 O.sub.3 = 3.2)                                                           1.02   0.92                                              K--Y(SiO.sub.2 /Al.sub.2 O.sub.3 = 3.2)                                                            1.10   0.85                                              Na--Y(SiO.sub.2 /Al.sub.2 O.sub.3 = 4.8)                                                           0.91   0.68                                              K--Y(SiO.sub.2 /Al.sub.2 O.sub.3 = 4.8)                                                            1.16   1.89                                              Ca--Y(SiO.sub.2 /Al.sub.2 O.sub.3 = 4.8)                                                           1.05   1.16                                              Na--X(SiO.sub.2 /Al.sub.2 O.sub.3 = 2.5)                                                           1.05   1.03                                              K--X(SiO.sub.2 /Al.sub.2 O.sub.3 = 2.5)                                                            1.20   0.78                                              Ca--X(SiO.sub.2 /Al.sub.2 O.sub.3 = 2.5)                                                           1.18   0.45                                              Ba--X(SiO.sub.2 /Al.sub.2 O.sub.3 = 2.5)                                                           0.89   1.61                                              Ag--Y(SiO.sub.2 /Al.sub.2 O.sub.3 = 4.8)                                                           1.38   0.99                                              ______________________________________                                    

COMPARATIVE EXAMPLE 2

The adsorbent of the K-Y type prepared in Example 1 was subjected to theion exchange treatment with an aqueous solution containing an ion otherthan potassium in an amount corresponding to 10 mole% of the potassiumcation in the adsorbent. The adsorptive selectivities of the resultingadsorbent for the chlorotoluene isomers were determined in the samemanner as described in Example 1. The obtained results are shown inTable 3.

                  TABLE 3                                                         ______________________________________                                        Adsorbent         α.sub.o/m                                                                      α.sub.p/m                                      ______________________________________                                        Ba--K--Y          1.18   2.15                                                 Mg--K--Y          1.16   2.04                                                 Ca--K--Y          1.22   1.61                                                 Sr--K--Y          1.15   1.54                                                 Co--K--Y          1.11   1.79                                                 ______________________________________                                    

EXAMPLE 3

Alumina sol was added as a binder to a powder of a zeolite of the Na-Ytype ("SK-40" supplied by Union Carbide Corporation) in an amount of 10%by weight as Al₂ O₃, a granulation product having a size of 24 to 32mesh was prepared by extrusion molding from the mixture. The granulationproduct was dried at 100° C. and calcined at 500° C. for 1 hour toprepare an adsorbent of the Na-Y type. Then, the adsorbent was treatedwith an aqueous solution of potassium nitrate to replace at least 90% ofthe sodium ion with potassium and thereby prepare an adsorbent of theK-Y type.

Then, the zeolite of the K-Y type was treated at 60° C. with an aqueoussolution of silver nitrate containing a silver ion in an amountcorresponding to 30 mole% of the K cation, whereby adsorbent of the 30%Ag-K-Y type was prepared.

In order to determine the adsorptive selectivities of theabove-mentioned 3 kinds of the adsorbents for DCB isomers, about 2 g ofthe adsorbent calcined at 500° C. for 1 hour and about 2.5 g of aliquid-phase mixture which comprises DCB isomers were charged in anautoclave having an inner capacity of 5 ml, and was then heated at 110°C. for 1 hour while conducting stirring now and then. A liquid phasemixture charged to the autoclave comprised n-nonane, p-DCB, m-DCB ando-DCB at a weight ratio of 1:1:3:3, respectively. n-Nonane was added asthe internal standard substance for the gas-chromatographical analysis,and n-nonane was substantially inactive relatively to the adsorption.The composition of the liquid phase mixture after the contact with theadsorbent was analyzed by the gas chromatography and the adsorptiveselectivities for the DCB isomers were determined according to the aboveformula. The obtained results are shown in Table 4.

                  TABLE 4                                                         ______________________________________                                        Adsorbent          α.sub.p/m                                                                      α.sub.o/m                                     ______________________________________                                        Na--Y              1.67   2.04                                                K--Y               1.54   2.33                                                30% Ag--K--Y       1.43   2.77                                                ______________________________________                                    

The adsorption selectivities of the above three adsorbents for the DCBisomers in the presence of a desorbent were determined. As thedesorbent, 3,4-dichlorotoluene (hereinafter referred to as "DCT") orchlorobenzene (hereinafter referred to as "CB") was chosen. The feed tobe contacted with the adsorbent comprised n-nonane, p-DCB, m-DCB, o-DCBand the desorbent at a weight ratio of 1:1:3:3:7, respectively. Otherconditions were the same as described above. The obtained results areshown in Table 5.

                  TABLE 5                                                         ______________________________________                                        Adsorbent  Desorbent      α.sub.p/m                                                                      α.sub.o/m                              ______________________________________                                        Na--Y      DCT            1.78   1.14                                         K--Y       CB             1.15   2.22                                         Ag--K--Y   DCT            1.50   2.80                                         Ag--K--Y   CB             1.54   4.34                                         ______________________________________                                    

As is apparent from the foregoing experimental results, the adsorbentsother than the adsorbent of the Ag-K-Y type according to the presentinvention have in the absence of the desorbent an adsorption selectivityas high as capable of recovering m-DCB from a mixture of DCB isomers,but in these adsorbents, under practical adsorption conditions, that is,in the presence of the desorbent, the value α_(p/m) or α_(o/m) is closeto 1 and separation of m-DCB from other DCB isomers is very difficult.In contrast, in case of the adsorbent of the Ag-K-Y type according tothe present invention, the adsorptive selectivity is not reduced even inthe presence of the desorbent and this adsorbent is very valuable forthe industrial separation of m-DCB.

COMPARATIVE EXAMPLE 3

Alumina sol was added as a binder to a powder of a zeolite of the Na-Xtype (SiO₂ /Al₂ O₃ molar ratio was about 2.5) or the Na-Y type (SiO₂/Al₂ O₃ molar ratio was 4.8 to 5.2) in an amount of 10% by weight as Al₂O₃, a granulation product having a size of 24 to 32 mesh was prepared byextrusion molding from the mixture. The granulation product was dried at100° C. and calcined at 500° C. for 1 hour to obtain an adsorbent of theNa-X or Na-Y type.

Then, the adsorbent was treated with an aqueous solution of potassiumnitrate to replace at least 90% of the sodium cation with the potassiumcation and thereby prepare an adsorbent of the K-X or K-Y type.

In order to determine the adsorptive selectivities of the adsorbent forxylenol isomers, about 2 g of the adsorbent calcined at 500° C. for 1hour and about 2.5 g of a liquid-phase mixture which comprises xylenolisomers were charged in an autoclave having an inner capacity of 5 ml,and was heated at 130° C. for 1 hour while conducting stirring now andthen.

The liquid phase mixture charged into the autoclave comprised 2,6-XYOH,2,4-XYOH, 3,5-XYOH 3,4-XYOH and n-nonane at a weight ratio of 1:8:1:1:3,respectively.

n-Nonane was added as the internal standard substance for thegas-chromatographical analysis, and n-nonane was substantially inactiverelatively to the adsorption under the experimental conditions.

The composition of the liquid phase mixture after the contact with theadsorbent was analyzed by the gas chromatography, and adsorptionselectivities α were determined. The obtained results are shown in Table6.

                  TABLE 6                                                         ______________________________________                                              α   α   α                                             Adsor-                                                                              3,5-XYOH/ 3,5-XYOH/ 3,5-XYOH/                                                                             Order of                                    bent  2,6-XYOH  2.4-XYOH  3,4-XYOH                                                                              Adsorbability                               ______________________________________                                        Na--X 1.26      2.32      0.76    3.4>3.5>2.6>2.4                             K--X  0.82      1.11      0.47    3.4>2.6>3.5≈2.4                     Na--Y 2.65      1.79      0.94    3.4≈3.5>2.4>2.6                     K--Y  0.82      1.10      0.44    3.4>2.6>3.5≈2.4                     ______________________________________                                    

The adsorbability of 3,5-XYOH to the above-mentioned adsorbents isintermediate among the adsorbabilities of the XYOH isomers. Accordingly,it is impossible to separate and recover 3,5-XYOH as the componentcapable of being most weakly adsorbed component, that is, the raffinatecomponent.

EXAMPLE 4

The adsorbents prepared in Comparative Example 3 were subjected to theion exchange treatment 5 times by using an aqueous 0.5N solution ofother cation. The solid-liquid ratio was 5 and the temperature was 90°C.

The obtained adsorbents were tested in the same manner as described inComparative Example 3. The obtained results are shown in Table 7.

                                      TABLE 7                                     __________________________________________________________________________           α                                                                              α                                                                              α                                                         3,5-XYOH/                                                                            3,5-XYOH/                                                                            3,5-XYOH                                                                             Order of                                          Adsorbent                                                                            2,6-XYOH                                                                             2,4-XYOH                                                                             3,4-XYOH                                                                             Adsorbability                                     __________________________________________________________________________    Oa--Na--X                                                                            1.30   1.55   0.67   3.4 > 3.5 > 2.6 > 2.4                             Li--Na--Y                                                                            2.06   1.24   0.65   3.4 > 3.5 > 2.4 > 2.6                             Ni--Na--Y                                                                            3.14   1.45   0.55   3.4 > 3.5 > 2.4 > 2.6                             Co--Na--Y                                                                            2.79   1.60   0.52   3.4 > 3.5 > 2.4 > 2.6                             Co--K--Y                                                                             1.36   0.98   0.59   3.4 > 3.5 ≈ 2.4 > 2.6                     Cu--Na--Y                                                                            0.55   0.51   0.35   3.4 > 2.4 ≈ 2.6 > 3.5                     Cu--K--Y                                                                             0.70   0.69   0.50   3.4 > 2.4 ≈ 2.6 > 3.5                     __________________________________________________________________________

Among the adsorbents shown in Example 4, only the adsorbents containingthe copper cation can separate and recover 3,5-XYOH having a high purityas the raffinate component.

EXAMPLE 5

The zeolite of the K-Y type prepared in Comparative Example 3 wassubjected to the ion exchange treatment with an aqueous solution ofsilver nitrate containing a silver ion in an amount corresponding to 20,30 or 40 mole% of the potassium cation in the zeolite. Some samples werefurther ion-exchanged with about 5 mole% of a proton (H). The adsorbentswere tested in the same manner as described in Comparative Example 3.The obtained results are shown in Table 8.

                                      TABLE 8                                     __________________________________________________________________________               α                                                                             α                                                                             α                                                           3,5-XYOH/                                                                           3,5-XYOH/                                                                           3,5-XYOH                                                                            Order of                                         Adsorbent  2,6-XYOH                                                                            2,4-XYOH                                                                            3,4-XYOH                                                                            Adsorbability                                    __________________________________________________________________________    20% Ag--K--Y                                                                             0.78  0.71  0.41  3.4 > 2.4 ≈ 2.6 > 3.5                    30% Ag--K--Y                                                                             0.81  0.80  0.50  "                                                30% Ag--(H)--K--Y                                                                        0.57  0.57  0.37  "                                                40% Ag--(H)--K--Y                                                                        0.69   .76  0.46  "                                                __________________________________________________________________________

The silver cation-containing adsorbents shown in this example canseparate and recover 3,5-XYOH having a high purity as the raffinatecomponent.

EXAMPLE 6

The adsorption selectivities of the copper or silver cation-containingadsorbents prepared in Examples 4 and 5 were determined by using amixture of XYOH isomers containing p- and m-ethylphenols (hereinafterreferred to as "EP").

The mixture comprised 2,3-XYOH, 2,4-XYOH, 3,4-XYOH, 3,5-XYOH, P-EP andm-EP at a weight ratio of about 5/5/25/55/5/5, respectively.

The obtained results are shown in Table 9.

                                      TABLE 9                                     __________________________________________________________________________                                 α                                                                             α                                               α                                                                             α                                                                             α                                                                             3,5-  3,5-                                                  3,5-XYOH/                                                                           3,5-XYOH/                                                                           3,5-XYOH/                                                                           XYOH/ XYOH/                                      Adsorbent  2,3-XYOH                                                                            2,4-XYOH                                                                            3,4-XYOH                                                                            p-EP  m-EP                                       __________________________________________________________________________    Cu--Na--Y  0.55  0.44  0.45  0.51  0.76                                       30% Ag--(H)--K--Y                                                                        0.24  0.28  0.30  0.16   .30                                       __________________________________________________________________________

As is apparent from the results shown in Example 6, the copper or silvercation-containing adsorbent according to the present invention canseparate and recover 3,5-XYOH as the raffinate component even ifethylphenols are contained in a mixture of XYOH isomers.

EXAMPLE 7

The adsorption selectivities of the 30% Ag-K-Y adsorbent containing a Agcation prepared in Example 3 were determined by using a mixture oftrimethylbenzene (hereinafter referred to as "TMB") isomers. The mixturecomprised 1,2,3-TMB, 1,2,4-TMB, 1,3,5-TMB and n-nonane at a weight ratioof 2/2/2/1, respectively. The testing temperature was 130° C. and allother conditions remained substantially the same as mentioned in Example1.

The obtained results are shown in Table 10.

                  TABLE 10                                                        ______________________________________                                                   α    α                                                            1,2,3-TMB/ 1,2,4-TMB/ Order of                                     Adsorbent  1,3,5-TMB  1,3,5-TMB  Adsorbability                                ______________________________________                                        30% Ag--K--Y                                                                             2.95       2.78        1,2,3--TMB                                                                   ≧1,2,4-TMB                                                             >1,3,5-TMB                                   ______________________________________                                    

The silver-cation containing adsorbent shown in this example canseparate and recover 1,3,5-TMB as the raffinate component.

COMPARATIVE EXAMPLE 10

The adsorption selectivities between TMB isomers of the Na-Y type andK-Y type adsorbents prepared in Example 3 were determined. The testingconditions were substantially the same as employed in Example 7.

The obtained results are shown in Table 11.

                  TABLE 11                                                        ______________________________________                                                 α     α                                                           1,2,3-TMB/  1,2,4-TMB/ Order of                                      Adsorbent                                                                              1,3,5-TMB   1,3,5-TMB  Adsorbability                                 ______________________________________                                        Na--Y    1.27        0.77        1,2,3-TMB                                                                    >1,3,5-TMB                                                                    >1,2,4-TMB                                    K--Y     1.00        2.30        1,2,4-TMB                                                                    >1,3,5-TMB                                                                    =1,2,3-TMB                                    ______________________________________                                    

EXAMPLE 8

The adsorbents of the Ag-K-Y type prepared in the same manner asdescribed in Example 1 were tested for the adsorptive selectivity of thediethylbenzene isomers. The liquid-phase mixture charged comprisedn-nonane, p-DEB, m-DEB and o-DEB at a weight ratio of 20/22/54/4. Theadsorptive selectivities of the resulting adsorbents for thediethylbenzene isomers were determined in the same manner as describedin Example 1. The obtained result are shown in Table 12.

                  TABLE 12                                                        ______________________________________                                        Amount of Ag Ion in Treating                                                  Liquid [Ag/(K--Y) molar ratio]                                                                      α.sub.o/m                                                                      α.sub.p/m                                  ______________________________________                                        0.1                   2.     1.                                               0.3                   1.     2.                                               0.4                   1.     1.                                               0.8                   1.     1.                                               ______________________________________                                    

COMPARATIVE EXAMPLE 11

The adsorbents of the Na-Y and K-Y prepared in Example 3 were tested inthe same manner as described in Example 8. The obtained results areshown in Table 13.

                  TABLE 13                                                        ______________________________________                                        Adsorbent         α.sub.o/m                                                                      α.sub.p/m                                      ______________________________________                                        K--Y              0.51   3.57                                                 Na--Y             1.22   0.84                                                 ______________________________________                                    

What is claimed is:
 1. A process for separating 1,3,5-trimethylbenzenefrom an isomer mixture containing 1,3,5-trimethylbenzene,1,2,3-trimethylbenzene and 1,2,4-trimethylbenzene which comprisescontacting the isomer mixture with an adsorbent of a zeolite of the Ytype containing at least one cation selected from the group consistingof an Ag cation and a Cu cation and at least one cation selected fromthe group consisting of an Na cation and a K cation, whereby1,3,5-trimethylbenzene is separated and recovered as a raffinatecomponent, and expelling the isomers adsorbed in the adsorbent by adesorbent to regenerate the adsorbent.
 2. A process according to claim1, wherein the Y type zeolite adsorbent contains at least one of the Agcation and the Cu cation in an amount of 5 to 100 mole% of all thecations.
 3. A process according to claim 1, wherein the desorbent is atleast one member selected from the group consisting of toluene, xyleneand diethylbenzene.